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GMAT Diagnostic Test Question 1 : Retired Discussions [Locked]

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Re: GMAT Diagnostic Test Question 1 [#permalink]
21 Dec 2009, 13:09

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Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

Re: GMAT Diagnostic Test Question 1 [#permalink]
14 Dec 2010, 20:22

2

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To add to lionslion's technique, if you already solved the square root of the first number to be 18 then by inspection you can tell that the second number has to be 17 and not 13 since square of 13 has to be closer to 100 (10sq = 100) whereas square for 17 has to be closer to 400 (20sq = 400). Since both 13 and 17 are primes, making a known guess would indeed save you tedious calculation on each one one of them. _________________

-DK --------------------------------------------------------- If you like what you read then give a Kudos! Diagnostic Test: 620 The past is a guidepost, not a hitching post. ---------------------------------------------------------

Re: GMAT Diagnostic Test Q1 [#permalink]
21 Dec 2009, 06:50

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I'd recommend remembering the squares of integers up to 20. You'll be able to save some time if you do. If you can't tell what the multiples of a number, you'll have to find them one by one. I doubt there's some magic technique for it .

sunnyvee wrote:

bb wrote:

Explanation:

Rating:

Official Answer: D

\sqrt{324} = 18; \sqrt{289} = 17; 18 + 17 = 35

this qxn may seem dumb, but what figures did you use for \sqrt{289}? plus cud u show shorter way of finding the multiples without having to calculate figure after figure? hope i make sense thank you

And it works for any number regardless if it is perfect square or not.

Thanks LU

What is this "Math formula" ? It works for any number? The square root of 64 + the square root of 25 is NOT equal to 64 - 25. Or what am I missing here?

Re: GMAT Diagnostic Test Q1 [#permalink]
21 Dec 2009, 05:21

bb wrote:

Explanation:

Rating:

Official Answer: D

\sqrt{324} = 18; \sqrt{289} = 17; 18 + 17 = 35

this qxn may seem dumb, but what figures did you use for [m]\sqrt { 289}? plus cud u show shorter way of finding the multiples without having to calculate figure after figure? hope i make sense thank you _________________

if someone was able to do it, this proves it can be done, and so is within reach = I CAN TOO

Re: GMAT Diagnostic Test Question 1 [#permalink]
29 Dec 2009, 01:42

lionslion wrote:

Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

cool. that sure helps _________________

if someone was able to do it, this proves it can be done, and so is within reach = I CAN TOO

Re: GMAT Diagnostic Test Q1 [#permalink]
11 Jan 2010, 20:37

dzyubam wrote:

I'd recommend remembering the squares of integers up to 20. You'll be able to save some time if you do. If you can't tell what the multiples of a number, you'll have to find them one by one. I doubt there's some magic technique for it .

sunnyvee wrote:

bb wrote:

Explanation:

Rating:

Official Answer: D

\sqrt{324} = 18; \sqrt{289} = 17; 18 + 17 = 35

this qxn may seem dumb, but what figures did you use for \sqrt{289}? plus cud u show shorter way of finding the multiples without having to calculate figure after figure? hope i make sense thank you

Memorizing squares of integers up to 20 is so worthwhile. Helped me get a quick and right answer. _________________

Re: GMAT Diagnostic Test Question 1 [#permalink]
16 Feb 2010, 06:26

lionslion wrote:

Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

to start the quiz with this question was a bummer for me, as i just simply stumped by looking at this question, wasted 90 secs to realise that the above startegy could do the job for me and was done in just over 2 mins. it does make sense to memorize squares upto 20 but even if you don't then just check for the unit digits and should do the job

Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

Re: GMAT Diagnostic Test Question 1 [#permalink]
30 Jan 2011, 12:00

'check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..'

this does make sense surely _________________

What is of supreme importance in war is to attack the enemy's strategy.

gmatclubot

Re: GMAT Diagnostic Test Question 1
[#permalink]
30 Jan 2011, 12:00